Add interpolation logic

src/lib.rs

@@ -1,13 +1,13 @@
 use std::fmt::Display;
 
 #[derive(Debug, Clone, Default)]
-pub struct InterpLUT<T> {
-    inner: Vec<(T, T)>,
+pub struct InterpLUT {
+    inner: Vec<(f64, f64)>,
 }
 
-impl InterpLUT<f64> {
+impl InterpLUT {
     /// Creates a new, empty table.
-    pub fn new() -> InterpLUT<f64> {
+    pub fn new() -> InterpLUT {
         Self::default()
     }
 
@@ -27,9 +27,42 @@ impl InterpLUT<f64> {
         self.inner.push((m, n));
         self.sort();
     }
+
+    fn binary_search(&self, n: &f64) -> Result<usize, usize> {
+        self.inner
+            .binary_search_by(|&(x, _)| x.partial_cmp(n).unwrap_or(std::cmp::Ordering::Equal))
+    }
+
+    pub fn get(&self, n: f64) -> Option<f64> {
+        let searched = self.binary_search(&n);
+        if let Ok(i) = searched {
+            return Some(self.inner[i].1);
+        } else if let Err(i) = searched {
+            // value was not found
+            if i == 0 || i == self.inner.len() {
+                return None;
+            }
+            let t = Self::inverse_lerp(self.inner[i - 1].0, self.inner[i].0, n);
+            let res = Self::lerp(self.inner[i - 1].1, self.inner[i].1, t);
+            return Some(res);
+        }
+        None
+    }
+
+    fn inverse_lerp(low: f64, high: f64, n: f64) -> f64 {
+        let total_distance = high - low;
+        let partial_distance = n - low;
+        partial_distance / total_distance
+    }
+
+    fn lerp(low: f64, high: f64, t: f64) -> f64 {
+        let total_distance = high - low;
+        let partial_distance = total_distance * t;
+        low + partial_distance
+    }
 }
 
-impl Display for InterpLUT<f64> {
+impl Display for InterpLUT {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let num_digits_largest = self
             .inner

src/main.rs

@@ -1,16 +1,16 @@
 use interplut::InterpLUT;
 
 fn main() {
-    let mut lut: InterpLUT<f64> = InterpLUT::new();
+    let mut lut = InterpLUT::new();
 
     lut.insert(31.0, 5.0);
-    lut.insert(5.0, 31.0);
-    lut.insert(5.0, 31.0);
-    lut.insert(5.0, 31.0);
-    lut.insert(4.0, 31.0);
-    lut.insert(3.0, 31.0);
-    lut.insert(2.0, 31.0);
-    lut.insert(1.0, 31.0);
+    lut.insert(5.0, 30.2);
+    lut.insert(4.0, 30.0);
+    lut.insert(3.0, 29.0);
+    lut.insert(2.0, 28.0);
+    lut.insert(1.0, 27.0);
     lut.insert(18.0, 31.0);
     println!("{}", lut);
+    dbg!(lut.get(0.5));
+    dbg!(lut.get(17.));
 }